Full adder based reconfigurable spintronic ALU using STT-MTJ

Abstract

Spin Transfer Torque-Magnetic Tunnel Junction (STT-MTJ) has some unique and attractive properties like non-volatility, scalability, very low access times, etc. Moreover, the critical switching current of STT-MTJ is found to reduce, as the device scales down. Nowadays, the semiconductor industry is unable to follow the Moore's law as miniaturization of CMOS is nearing its limit due to the enormous increase in leakage currents. Hence, STT-MTJ with better features has the capability of replacing conventional CMOS transistors in the future. In this work, we design a reconfigurable full adder using the majority logic, which can act as an ALU. For this, we design a sum generator and a carry generator using MTJs and CMOSFETs. CMOS transistors switch the mode of operation of the sum generator and the carry generator from writing phase to reading phase and vice versa. During writing phase, input current pulses pass through MTJs which change MTJs' magnetization direction. During the reading phase, based on MTJs' magnetization direction, the output logic is interpreted. We show that, the full adder can be reconfigured to perform various arithmetic and logical operations. Our proposed reconfigurable spintronic ALU, can perform arithmetic operations like addition and subtraction, and various logical operations like AND, OR, NAND, NOR, NOT, XOR and XNOR using which a non-volatile digital system can be realised.